1. Technical Field of the Invention
The present invention relates to a droplet discharging apparatus and method for discharging droplets toward a target object by using a piezoelectric element, a film manufacturing apparatus and method using the droplet discharging apparatus and method, a device manufacturing method, and electronic equipment.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 7-304168 discloses an ink injection apparatus as an example to which a droplet discharging apparatus has been applied. The ink injection apparatus is adapted to transmit the operating heat of a drive circuit (IC chip) to an inkjet head (recording head) to set the ink temperature at an appropriate level so as to stabilize discharging characteristics. In other words, according to the conventional technology, the heat generated by the operation of the drive circuit is transmitted to the inkjet head thereby to heat the ink, then the hot ink is discharged. Thus, the drive circuit is cooled without the need for providing a heat sink or the like.
However, in the droplet discharging apparatus using piezoelectric elements, the mechanical loss caused by the oscillation of the piezoelectric elements generates heat (operating heat). The operating heat heats a discharge liquid, such as ink, leading to reduced liquid viscosity, which causes the problem of failure in obtaining a specified ink weight, the occurrence of satellites or reduced ink droplet diameters or crooked ink flight. No effective solutions to such problems have been found so far. Maintaining a discharge liquid at a certain temperature is important for securing stable discharge (stable quality). Efforts have been made to alleviate the problems described above by detecting the approximate temperature around a discharge liquid and by changing a head drive voltage or waveform. However, an inkjet head would have to be provided with a complicated additional mechanism to solve the problem of the discharge liquid being heated by the operating heat. This is not a good solution, judging from the aspect of cost or reliability. Hence, there has been a demand for a solution that makes the most of the existing mechanism without adding a new mechanism.